A storage medium is quite accurate and fragile, where the record areas and marks may be easily damaged and then the information written or read therein may be influenced and defective due to the falling dust, the scratches and even an improper writing thereto. Typically, upon receiving a reading command from a host, the reading device may accordingly start to seek through the storage medium for the area address to be read, and then decode the information of the area address, so as to execute the reading command.
Regarding the reading method disclosed in the Japan Pat. Pub. No. 11-7706, when the defect areas are found during a data reading operation, the defect areas skipping technique will be performed. The respective defect areas of the storage medium will be skipped and not be read until all of the normal areas are read. In this case, the normal areas would be read first, whereby the access time would be decreased. In the previous technology, the situation, which defect areas could be neglected in the first searching, can not be avoided. Thus, it needs to execute a second searching for the defect areas, this still results in time consumption.
Further schemes for reading the defect data written in the storage medium are also developed in this technology. For instance, the host may require the reading device of the storage medium to keep on seeking for the address of a target area, or to suspend the seeking while there is an error existing in seeking for the address of the area or in decoding the data written therein. In the case that the host requires the reading device to keep on seeking for the address, it would take the reading device extra time to seek for the respective addresses of all areas in the storage medium again, which is followed by a decoding operation. Moreover, if there is still an error existing in the decoded data, the host may require the reading device to re-seek for the address, and then the decoding operation is also re-performed. Consequently, the whole system may keep on and thus take much time to perform the cycle of address seeking and data decoding. Even though the host requires the reading device to suspend the seeking of the defect areas or erroneously decoded area upon the present reading, the defect areas as well as the erroneously decoded area will still to be read the next time. Therefore, the above-stated method also fails to decrease the total access time for the storage medium.
As for the data decoding for the audio and/or video medium, it is more important to enhance the continuity of signal displaying and the decoding efficiency, rather than reading out the data written in defect areas. Therefore, it is desirable to have an improved method and apparatus for decreasing the time consumed in seeking for the defect areas and for increasing the efficiency of reading the data written in the storage medium.